<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
    <title>Document</title>
    <style>
        .first{
            width: 100px;
            height:100px;
            background-color: red;
        }
        .then{
            width: 200px;
            height:200px;
            background-color: greenyellow;
        }
        .last{
            width: 300px;
            height:300px;
            background-color: navy;
        }
        .active{
            color:red;
        }
    </style>
</head>
<body>
<div id="app">
    <div :class=['one','two','three']></div>

    <div class="public" :class="boxClass">test</div>


</div>
<script>
    const vm = new Vue({
        el:'#app',
        data(){
            return{

                boxClass:['one','two','three']
            }
        }
    })
</script>
</body>
</html>